During Story of Eastern Wonderland, Rika, for whatever reason, created a large number of monsters and started hanging around the Hakurei Shrine while Reimu was away. Exactly how Rika created "monsters" and "ghosts" isn't clear, but she seems to have engineered a few tanks as well. After being defeated she tried luring Reimu into a trap, but Reimu's natural intuition won out and she didn't fall for it. Rika came back later with a flying tank, Evil Eye Sigma.